1. Technical Field
The present invention relates to a test apparatus and a probe card. In particular, the present invention relates to a test apparatus that tests a wafer or the like having a connection terminal, as a device under test, and to a probe card mounted thereto.
2. Related Art
In a wafer test in which a semiconductor circuit or a semiconductor device (DUT) and the like is tested in a wafer form, a component referred to as “probe card” is used for providing electrical connection to minute connection terminals on the wafer. A probe card is positioned between a device under test and a test apparatus to provide electric connection to them.
A probe card has probe pins to abut against minute connection terminals of a device under test, for allowing electrical connection. In addition, a probe card has pads and the like to abut against spring pins provided for a semiconductor test apparatus. According to them, a device under test and a test apparatus are electrically connected to each other, without trouble of removing/mounting or plugging/unplugging of connectors and so on.
The probe card is exchangeable in most test apparatuses. Moreover, many types of devices under test can be tested using a single test apparatus, by preparing many types of probe cards corresponding to the number of specifications of the devices under test.
Japanese Patent Application Publication No. 08-306750 proposes usage of, in a wafer test apparatus, a probe card equipped with a function of diagnosing the test apparatus itself (self-diagnosis function), in an effort to provide the test apparatus with a variety of functions using a probe card, which is small and easy to exchange.
Japanese Patent Application Publication No. 09-298223 discloses a test apparatus to which probe cards of different sizes are mounted, thereby increasing the types of probe cards mountable to the test apparatus, further enhancing the availability of the test apparatus.
Recently, as devices under test have been improved to have advanced functions, the number of connection terminals formed on a wafer, i.e., a device under test, is noticeably increasing. Test apparatuses are also being equipped with improved performance and advanced functions, to conduct a plurality of types of tests simultaneously. Consequently, there is a demand to increase the number of signal transfer paths to a device under test, so as to improve the throughput of a test.
If the number of connection terminals in a device under test is increased, the number of probe pins mounted to a probe card also increases. The probe pin itself is a minute element, and the probe card is sufficiently smaller than a device under test. Therefore, the device under test can still maintain connection even if the number of connection terminals has increased, by simply increasing the number of probe pins.
With respect to the connection between the probe card and a test apparatus, however, space allocation is becoming a problem. Specifically, spring pins widely used for connecting a test apparatus to a probe card has such a movable structure that is biased in an elongating direction and is shortened when abutting against a pad. Therefore, a spring pin has to have a certain thickness.
Moreover, some probe cards have spring pins shaped as needles or as bars, which repeat being in contact with and apart from the pads as the test apparatus is used. For this reason, a pad is required to have a width or a space sufficient for the thickness of a spring pin.
The above requirements impose limitation on the number of signal transfer paths formed between a test apparatus and a probe card, which hinders improvement in throughput of a test apparatus. For other things, a device under test that has a tremendously large number of connection terminals requires an expensive dedicated test apparatus. An example of such device under tests having many connection terminals is a driving circuit for liquid crystal display devices which have recently been widely produced.